Friday September 17 2010
Supplements did not reduce pain or affect joint structure
Supplements to ease the pain of arthritis “do not work”, reported The Independent. The newspaper said that the supplements glucosamine and chondroitin, which are “widely sold in health shops and have increasingly been prescribed by GPs and rheumatologists in the last decade”, are no better than placebo at reducing joint pain.
The news story is based on research that pooled data from 10 trials and found that chondroitin, glucosamine or a combination of the two were not useful in reducing the joint pain or treating the narrowing of the joint space associated with osteoarthritis. However, the supplements were not shown to be harmful.
This was a well-conducted study and its results are in keeping with guidance from the National Institute for Health and Clinical Excellence (NICE), which does not recommended treating osteoarthritis with these supplements.
Where did the story come from?
The study was carried out by researchers from the University of Bern, Switzerland, and was funded by the Swiss National Science Foundation. It was published in the peer-reviewed British Medical Journal.
This study was reported appropriately by the newspapers.
What kind of research was this?
This systematic review and network meta-analysis looked at whether the supplements glucosamine and chondroitin could help with joint pain associated with osteoarthritis of the hip or knee.
What did the research involve?
The researchers conducted their systematic review by searching scientific and medical databases for terms related to osteoarthritis and the generic and trade names of chondroitin and glucosamine. They also searched conference proceedings, text books, reference lists from the journal articles that they found and contacted experts in the field.
They included randomised controlled trials with at least 200 patients with hip or knee osteoarthritis which was treated with either glucosamine, chondroitin or both. They excluded studies that used sub-therapeutic doses (less than 800mg a day of chondroitin and less than 1,500 mg a day of glucosamine).
The outcomes they looked at were pain intensity, joint structure assessed by radiography and side effects. Two of the four reviewers assessed the quality of the trials and only included trials in which the patients did not know whether they were receiving the treatment or the placebo.
The analysis of data was by network meta-analysis. This is a relatively new statistical technique that enables researchers to combine the results of trials and trial arms, comparing different treatments against each other and placebo-controlled trials within a single analysis.
Studies that had reported pain intensity used a visual analogue pain scale. This means that the participants rated their pain based on a 10cm scale. The researchers pre-determined that the minimum clinically important difference between preparations and placebo was a difference of 0.9cm on this 10cm scale.
What were the basic results?
The review contained 12 reports describing 10 trials that met the inclusion criteria.
The 10 trials had randomly allocated a total of 3,802 patients to receive either chondroitin or glucosamine (or both) and compared them with each other or placebo. Seven of the ten studies were funded by the supplement manufacturers.
The average age of the patients was between 58 and 66 years. The studies followed up the patients for between 1 and 36 months.
Participants receiving glucosamine ranked their pain 0.4cm lower on the pain scale than those taking a placebo. Chondroitin patients ranked their pain 0.3cm lower and participants that received both chondroitin and glucosamine ranked their pain 0.5cm lower than placebo. These differences were not clinically important as pre-specified by the researchers.
Six studies reported changes in joint structure assessed by radiography. It is known that osteoarthritis causes the space between affected joints to become narrower. Compared with placebo, chondroitin increased joint space by 0.2mm, glucosamine by 0.1mm and a combination of chondroitin and glucosamine resulted in no change.
There was no difference in the risk of side effects in participants receiving chondroitin or glucosamine, a combination of the two or placebo.
How did the researchers interpret the results?
The researchers said: “Chondroitin and glucosamine have been recommended in guidelines and have been prescribed by general practitioners and rheumatologists and used by patients as over the counter medications for osteoarthritis.” They also say that “results from randomised trials about the effectiveness of chondroitin are conflicting.” They say their meta-analysis showed that chondroitin, glucosomine and a combination of the two do not have a clinically relevant effect on perceived joint pain or on joint space narrowing. They also add that “estimated differences between supplements and placebo were less pronounced on average in industry independent trials and estimated treatment effects in industry independent trials were small or absent and clinically irrelevant.”
This systematic review and meta-analysis found that chondroitin, glucosamine or a combination of both do not have a useful clinical effect in the treatment of osteoarthritis. The supplements were also not found to be harmful. This study benefited from an extensive search for studies on these supplements, and made good use of all the data available by combining results in the network meta-analysis.
However, as with all meta-analyses, the studies included varied in a number of ways, including the severity of the osteoarthritis studied, the main joint involved, or how long the patients were followed up for. This is called heterogeneity. Using the network meta-analysis, the researchers were able to combine evidence from different comparisons of the supplements. This means that the heterogeneity was more complex to calculate, but the researchers say it was low enough to allow them to combine the trials reliably.
A meta-analysis was needed as the randomised controlled trials involving these supplements were small. While it appears from this study that the effects of these supplements are limited, a small effect in a small group of patients could have had a relatively large effect on the overall results. A large randomised controlled trial on a clinically defined group of patients is the best way to assess the effectiveness of these treatments.
Glucosamine and chondroitin are not currently part of the treatment strategy for osteoarthritis recommended by NICE. Patients should consult their GP about the best pain-management options available to them.